The present invention relates to a machine for beading cans or can bodies of cylindrical shape, a particular feature of which is that the cans are conveyed in an upright position and maintained thus throughout the beading operation.
The operation of beading cylindrical tin cans or can bodies consists in deforming the cylindrical wall of the empty can to the end of investing it with increased strength and rigidity.
Conventionally, the operation is effected utilizing machinery that incorporates a revolving head or carousel rotated through at least two stations, one of which feeding in unbeaded cans, and another from which the beaded cans run out.
The revolving head comprises a plurality of work stations, each comprising fixed means by which to support a respective can or can body, and means (a mandrel) by which to constrain and forcibly deform the cylindrical wall. The machine also comprises reaction means positioned between the infeed and runout stations, considered in the direction of rotation of the revolving head, which are embodied as a sector to a cylinder and designed to interact with the constraint means; also, means located at the infeed and runout stations serving respectively to transfer the cans onto and to distance them from the support means of the revolving head.
The support means consist in a surface on which to set the can, and at least one element affording a substantially semicylindrical surface of diameter marginally greater than that of the production can body to be beaded.
Constraint and forcing means at each work station consist in a cylindrical mandrel, coaxial with the semicylindrical surface of the support means and of diameter marginally less than that of the can body to be beaded: thus, each mandrel combines with the relative support means to afford a semicylindrical interstice in which the can wall is accommodated. The mandrel is capable of movement in relation to the support means between a lowered position, which allows the can to be set on the support means, and a raised position of full insertion into the can. In effect, the mandrel is capable of movement in opposite directions through a distance not less than the height of the can to be beaded.
The mutually opposed surfaces of the single mandrel and the reaction means are complementarily shaped, and reflect the selected geometry of the beading to be reproduced by rotation of the mandrel against the reaction surface.
A machine structured after this fashion betrays numerous drawbacks, first among which being that of its inability to adapt to different sizes of cans. Supposing, for example, that the diameter of the can to be beaded is smaller than that for which the machine was last set up, the mandrels and supports must all be replaced with others of suitable size. Thereafter, to ensure proper contact between the wall of the can and the surfaces of the mandrel and the reaction sector on either side, the clearance between mandrel and sector must also be adjusted; this operation is effected either by altering the position of the mandrels or by replacing or moving the reaction sector.
The facility of repositioning the mandrels, hence of altering the circular trajectory described by their axes, obviously must imply a considerably complex structure of the revolving head and a more expensive machine overall.
Replacement of the reaction sector is certainly the more economic option, though in the event that the change sector is of radial depth equal to that of the sector removed, it must be positioned closer to the axis of the revolving head.
At all events, the beading of different size cans, however slight the dissimilarity in diameter to be accommodated, conventionally involves a lengthy replacement of parts and change gears that is both time-consuming, and costly as regards equipment. Functionally, the machine is beset by the drawback that its operating speed may be limited, especially with larger cans; the taller the production can, in fact, the greater the distance the mandrel has to cover on insertion and withdrawal, hence the longer the time required.
A further drawback stems from the inability of the machine to operate with a number of mandrels less than that for which the revolving head is designed. Thus, a user who has no requirement for especially high operating speeds is obliged to purchase a machine having the full set of mandrels, sectors and support means, which must then be operated at a speed lower than the nominal. In short, the outlay on such a machine reflects a heavy investment for the manufacturer operating at relatively low output levels, and a longer amortization period than would normally be the case.
Accordingly, the object of the present invention is to provide a beading machine responding to the type described above, but affording greater flexibility in such a way as to handle different can sizes and enable operation at high and low speeds alike.